Radiation Therapy Photon Beams Dose Conformation According to Dose Distribution Around Intracavitary-Applied Brachytherapy Sources

• Published in: Medical dosimetry : official journal of the American Association of Medical Dosimetrists Vol. 35; no. 1; pp. 49 - 52
• Main Authors: Jurković, Slaven, M.Sc, Žauhar, Gordana, Ph.D, Faj, Dario, Ph.D, Radojčić, Ðeni Smilović, B.Sc, Švabić, Manda, B.Sc
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 2010
• Subjects: BRACHYTHERAPY; Brachytherapy - instrumentation; Brachytherapy - methods; CARCINOMAS; Combined Modality Therapy; Compensators; Computer Simulation; FILM DOSIMETRY; Hematology, Oncology and Palliative Medicine; Humans; Models, Biological; PHOTON BEAMS; Photons - therapeutic use; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; Radiation therapy; Radiology; RADIOLOGY AND NUCLEAR MEDICINE; Radiometry - methods; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted - methods; Radiotherapy, Conformal - methods; SENSITIVITY; SHIELDING; UROGENITAL SYSTEM DISEASES; Compensators; Radiation therapy
• ISSN: 0958-3947; 1873-4022
• DOI: 10.1016/j.meddos.2009.01.006

Abstract Intracavitary application of brachytherapy sources followed by external beam radiation is essential for the local treatment of carcinoma of the cervix. Due to very high doses to the central portion of the target volume delivered by brachytherapy sources, this part of the target volume must be shielded while being irradiated by photon beams. Several shielding techniques are available, from rectangular block and standard cervix wedge to more precise, customized step wedge filters. Because the calculation of a step wedge filter's shape was usually based on effective attenuation coefficient, an approach that accounts, in a more precise way, for the scattered radiation, is suggested. The method was verified under simulated clinical conditions using film dosimetry. Measured data for various compensators were compared to the numerically determined sum of the dose distribution around brachytherapy sources and one of compensated beam. Improvements in total dose distribution are demonstrated, using our method. Agreement between calculation and measurements were within 3%. Sensitivity of the method on sources displacement during treatment has also been investigated.